The present invention relates to a contact pin for an electrical connector.
Multi-pin electrical connectors generally comprise a large number of contact pins, each of which comprises a connecting end intended to co-operate with the connecting end of a contact pin of an associated multi-pin connector and a joining end intended to receive the lead of an electrical cable which is soldered, brazed or wrapped onto that end.
Contact pins are routinely produced in two parts, namely a front part constituting the connecting end and a rear part constituting the joining end, to enable different materials with suitable elastic and plastic properties to be used.
With such contact pins, a problem arises when interconnecting the front and rear parts, since said coupling must be carried out simply and rapidly and must result in good electrical contact by introducing a minimum amount of disturbance to the electrical signal transmitted by the pin.
The present invention aims to provide a novel contact pin formed in two parts which constitutes an original solution to the above problem.
A contact pin for an electrical connector is also Known from GB-A-2 274 749 or U.S. Pat. No. 4,780,097, comprising a body, a connector element, and a sheath, the connector element being maintained in an extension of the body by being coupled with a peg projecting from the front face of the body, the sheath being disposed around the connector element and maintained on the body by clamping to an annular portion of said body.
The present invention provides a contact pin of that type, wherein, on the peg side, the connector element comprises an end for coupling with the peg, conformed such that the peg cannot fit inside the cross section of said coupling end, the connector element being capable of deforming elastically to enable its coupling end to be friction fitted onto the peg, the thus deformed connector element being unable to fit inside the cross section of the sheath, and wherein the sheath and the peg are separated by a clearance which is larger than the thickness of the wall of the coupling end of the connector element.
In other words, in the contact pin of the invention, the connector element is imprisoned between the peg, which is integral with the body, and the sheath under conditions such that said connector element is elastically constrained by the peg and the sheath.
Since the sheath is actually firmly fixed to the body by a forced friction fit onto an annular portion of the body, the result is that the mechanical link between the connector element and the remainder of the contact pin is particularly reliable.
It should be understood that because the connector element undergoes elastic deformation only when it is placed in position between the peg and the sheath, the forces which are exerted firstly between the connector element and the sheath, and secondly between the connector element and the peg are due to the resilience of the connector element.
In other words, the connector element does not suffer plastic deformation which would reduce the forces which it exerts on the sheath and the peg by resilience.
A further essential advantage of the contact pin of the invention is that it can tolerate relatively high manufacturing tolerances, since the elasticity of the connector element can to a large extent compensate for any defects in dimensioning between the parts.
Thus, taking the manufacturing tolerances of the body of the connector element and the sheath into account, in a preferred embodiment, the contact pin of the invention can be defined as satisfying the following conditions:
DText.maxxe2x89xa6DSmin
DSminxe2x88x92DPmaxxe2x89xa72xc2x7emax
DTint.max less than DPmin
DPminxe2x88x92DTint.max greater than DSmaxxe2x88x92DText.min
where:
DText.max is the maximum outside diameter of the connector element, taking manufacturing tolerances into account;
DText.min is the minimum outside diameter of the connector element, taking manufacturing tolerances into account;
DTint.max is the maximum inside diameter of the connector element, taking manufacturing tolerances into account;
emax is the maximum thickness of the connector element, taking manufacturing tolerances into account;
DSmin is the minimum inside diameter of the sheath, taking manufacturing tolerances into account;
DSmax is the maximum inside diameter of the sheath, taking manufacturing tolerances into account;
DPmax is the maximum outside diameter of the pin, taking manufacturing tolerances into account;
DPmin is the minimum outside diameter of the pin, taking manufacturing tolerances into account.
It goes without saying that the possibility of automatically compensating for manufacturing tolerances by the arrangement of the contact pin of the invention enables its different component parts to be manufactured employing simple and cheap manufacturing methods while the electrical qualities of the pin remain good.
In a particular embodiment of the invention, the connector element is dimensioned to allow it to slide freely in the sheath before undergoing the deformation resulting from friction fitting its coupling end on the peg.
In a preferred embodiment, the connector element has a longitudinal slot which enables it to pass from a closed position, in which the two edges of said slot touch each other, to an open position in which the two edges of said slot are spaced from each other, this open position resulting from deformation of said connector element
Preferably, the connector element is in its closed position before undergoing the deformation resulting from friction fitting its coupling end on the peg.
Thus after positioning the sheath, the connector element is in a position which is close to its closed position, the two edges of the slit almost touching, with the result that once the connector element is in place in the contact pin, its shape can remain stable even after a large number of connections/disconnections, because only the interface portion proper deforms elastically.
In general, as is the case in the majority of known contact pins, the body, the connector element, and the sheath of the pin of the invention are all substantially bodies of revolution.
In a particular embodiment, the coupling end of the connector element has a circular cross section with an inside diameter which is smaller than the inside diameter of the circular cross section of the remainder of the connector element.
The present invention also provides a method of assembling a contact pin as described above.
Such a method consists in friction fitting the coupling end of the connector element on the peg of the pin body, then aligning the sheath with the deformed connector element, the sheath being maintained in a sleeve having inside dimensions which correspond substantially to the outside dimensions of the sheath, engaging the sheath maintained in the sleeve around the connector element using an axial translation movement until the sheath has completely overlaid the connector element, then displacing the sheath from the sleeve by keeping the sleeve stationary so as to bring said sheath to the annular portion of the body by axial translation, before retracting the sleeve.
The essential advantage of this method is that it comprises axial translation operations only, which facilitates automation.